[Fleet] Add service name to datasets

[jalvz]

• Depends on spec definition
• Depends on kibana support
• Should rely on existing code to sanitize service name

[axw]

Confirmed with BC2 and epr-snapshot, with opbeans-python and opbeans-go running:

apm-integration-testing$ ./scripts/compose.py start 7.12 --bc=latest --apm-server-managed --with-elastic-agent --package-registry-url=https://epr-snapshot.elastic.co --with-opbeans-python --with-opbeans-go

The "-" in the service names, which is a reserved character (data stream separator) is replaced with "_".